Sewers were widely used by polish soldiers during the '44 warsaw uprising, as hiding places and transport routes. they were unsanitary, but being in an unsanitary place is better than being dead. so, i think that it could be done.

Mines aren't demolitions. And why would you want to do that? It'd be a waste of time, resources, cause more stuff to repair when it's all over, and make any roads on the surface impossible to drive on.

Storm drains are almost never big enough to be used comfortably. You'd have to be crawling through pitch-black pipes with who knows what kind of debris, and you'd have to do it with whatever gear you have on you, and God help you if you misfire or shoot in that pipe because it is going to ricochet everywhere.

as an effective means of travel? No. but the storm drains by the Bow river are like... have this bit concrete opening and a big grated pipe. I think THOSE are for people and the sewers are for poop and dead fish. too small for people.

I don't think most storm drains are made for people to enter. I think they're designed so that you have to dig up the ground over it to work on it. Either way, a storm drain would only be a viable method of transportation in an emergency, and if you had little to no gear on you. But still, you'd have to worry about debris, POSSIBLE zombie crawlers, small animals, and not getting lost. I would avoid them unless I had no other option.

Just the idea of escaping a zombie Apocalypse underground is horrifying. living in the dark earth, not seeing the sun shine or hear the wind passing by. Just shitting, eating and sleeping in the dark, crawling on all fours like a creature through tunnels in the dark or even by flashlight. All of that is enough to wish for a swift death when it came to it.

My question wasn't about dwelling in the sewers, but using them as an escape route.

Sorry, I missed the point of the topic

I mostly agree with the other posters : you have to know where you are going, have the fewest things possible on you... and even if you are less likely to run into a zombie, the smallest encounter would be deadly with the near-zero mobility and no easy escape.

The best weapon in my opinion would be something like a makeshift spear which could be used when crawling (a construction rod or a big pointy stick maybe ?)... the more I think of it, the more I find that engaging a combat in a storm drain/sewer would be very hard...